A. Field of the Invention
The present invention relates generally to a method and apparatus for electrically heat welding of thermoplastic fittings, and, more particularly, to an alternating current (AC) battery-powered apparatus for electrically heat welding of thermoplastic fittings, and method of using the same.
B. Description of the Related Art
Electric heat-weldable fittings (also known as electrofusion fittings) formed of thermoplastic materials have been developed and used heretofore. Such fittings generally include an electrically resistant heating coil or element positioned adjacent the inside surfaces of the fitting which are to be welded to one or more other thermoplastic members, such as plastic pipe sections. The electrically resistant heating element typically comprises a coil of resistance wire disposed in the thermoplastic material of the fitting, and connects to electric contacts attached to an outside surface of the fitting. Examples of such electric heat weldable thermoplastic fittings are described in U.S. Pat. Nos. 4,147,926 and 4,349,219.
Electrofusing is an effective method of installing branch connections or tapping into a main gas pipeline. Many vendors supply electrofusion fittings, wherein each of the fittings has a particular fusion voltage and fusion time. Many of the vendors have a proprietary method for identifying the fitting to be fused or for controlling the fusion process parameters such as time and voltage applied to the fitting, forcing a user to purchase a dedicated fusion system as well as the fittings from the vendor. This marketing method prohibits the user from purchasing electrofusion fittings competitively from all suppliers.
A method of identifying the electrofusion fitting and setting the correct fusion voltage and time is described in U.S. Pat. No. 4,837,424. This method allows the user to purchase electrofusion fittings competitively from all suppliers. A conventional electrofusion system 1 utilizing this method is shown in FIG. 1. In the conventional system, an electrofusion fitting 2 contains electrically resistive elements 3 embedded near the surface of the fitting. Power is supplied from a gasoline engine-powered AC generator or a battery-powered inverter 4. The system converts this power to a fixed AC voltage and supplies the fixed AC voltage to electrofusion fitting 2 through a pair of wires 5. A barcode wand or magnetic card reader 6 is used to scan machine readable data regarding fitting 2. This data is used to program the electrofusion system 1 with the proper fusion time and output voltage. When the user starts the fusion, an AC voltage is supplied to resistive element 3 in electrofusion fitting 2. Resistive element 3 generates heat, and the molten plastic then fuses and permanently joins electrofusion fitting 2 to a pipe 7, forming a leak tight joint. When the fusion time expires, electrofusion system 1 stops the AC voltage and terminates the fusion. Data from the fusion, including, an electrofusion system serial number, fusion number, fusion date and time, fitting manufacturer, fitting type, fitting size, ambient temperature, fusion voltage, nominal fusion time , adjusted fusion time (compensated for ambient temperature), actual time fused, fusion result, operator, location, and an information field, is stored in the internal memory of electrofusion system 1, along with the fusion mode, i.e. barcode or manual mode. This data may be downloaded at a later time to provide complete fusion traceability.
Conventional electrofusion system 1 is also equipped with systems to monitor the performance of the fusion as it progresses, and to terminate the fusion if abnormalities are found. Abnormalities include, but are not limited to, shorts in the fitting, low or high output voltage, insufficient supply voltage, disconnection of the fitting during fusion, or stoppage of the fusion by the user. The absence of errors indicates that the fusion was done properly. This system and method suffers from several problems. For example, this fusion system must be equipped with a barcode or magnetic card reader, devices which are not reliable in the field and which inconvenience the user when they fail.
Another conventional electrofusion system and method, described in U.S. Pat. No. 5,951,902, is powered by a direct current (DC) power source and supplies a direct current voltage output to the resistive element. This system also suffers from a variety of problems. For example, the DC voltage does not vibrate the fitting like the magnetic fields generated by an AC voltage (as described in U.S. Pat. No. 4,684,789). Since all electrofusion fittings are tested for proper performance and certified with an AC voltage, the electrofusion fittings may have to be re-characterized and certified with a DC voltage if the system of U.S. Pat. No. 5,951,902 is used. Another problem with this system is that fusion can begin even when there is insufficient energy in the battery to complete the fusion. This reduces the economic viability of electrofusion because the incomplete fusion must be replaced, and increases the possibility that an operator may not replace the faulty joint, resulting in a potentially lethal situation of a natural gas leak. Still another problem with this system is the lack of data storage available for traceability. This prevents analysis of fusion data to determine whether all fusions were completed without errors.
An object of the invention is to provide an apparatus and method for creating an electrofusion between thermoplastic members that overcomes the problems set forth above with respect to the related art.
A further object of the invention is to provide an easy to use apparatus and method that ensures safe, effective electrofusion between thermoplastic members.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be learned from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention comprises a method for creating an electrofusion between a plurality of thermoplastic members, wherein at least one of the members has an electrically resistive element embedded therein, the method including the steps of: generating an alternating current voltage from a direct current power supply; transmitting the alternating current voltage to the electrically resistive element; and regulating the alternating current voltage transmitted to the electrically resistive element at a predetermined alternating current voltage.
To further achieve the objects, the present invention comprises an apparatus for creating an electrofusion between a plurality of thermoplastic members, wherein at least one of the members has an electrically resistive element embedded therein, the apparatus comprising: a direct current power supply; means for generating an alternating current voltage from the power supplied by the power supply; means for transmitting the alternating current voltage to the electrically resistive element; and means for regulating the alternating current voltage transmitted to the electrically resistive element at a predetermined alternating current voltage.
To achieve these objects, the present invention also comprises a method and an apparatus for creating an electrofusion between a plurality of thermoplastic members, wherein at least one of the members has an electrically resistive element embedded therein, the apparatus comprising: means for identifying the thermoplastic member having the electrically resistive element embedded therein by measuring the resistance of the electrically resistive element; a programmable electronic data processing means for executing programmed arithmetic and logical processes and storing data, wherein the data processing means compares the resistance to a data table stored in the data processing means, and sorts duplicate fittings by the most frequently-used fitting; means for generating an alternating current voltage from a direct current power supply; and means for transmitting the alternating current voltage to the electrically resistive element.
To further achieve these objects, the present invention comprises a method and an apparatus for creating an electrofusion between a plurality of thermoplastic members, wherein at least one of the members has an electrically resistive element embedded therein, the apparatus comprising: means for identifying the thermoplastic member having the electrically resistive element embedded therein by measuring the resistance of the electrically resistive element; a programmable electronic data processing means for executing programmed arithmetic and logical processes and storing data, wherein the data processing means compares the resistance to a data table stored in the data processing means, and sorts duplicate fittings by the most frequently-used fitting; means for generating a voltage from a power supply; and means for transmitting the voltage to the electrically resistive element.
Another feature of the present invention and further in accordance with the objects, the present invention comprises a method and apparatus for creating an electrofusion between a plurality of thermoplastic members, wherein at least one of the members has an electrically resistive element embedded therein, the apparatus comprising: a programmable electronic data processing means for executing programmed arithmetic and logical processes and storing data, wherein the data processing means checks that sufficient energy is available in a direct current power supply to provide enough energy to the electrically resistive element to complete the electrofusion; means for generating an alternating current voltage from the direct current power supply; and means for transmitting the alternating current voltage to the electrically resistive element.
Still another feature of the present invention and further in accordance with the objects, the present invention comprises a method and an apparatus for creating an electrofusion between a plurality of thermoplastic members, wherein at least one of the members has an electrically resistive element embedded therein, the apparatus comprising: a programmable electronic data processing means for executing programmed arithmetic and logical processes and storing data, wherein the data processing means checks that sufficient energy is available in a power supply to provide enough energy to the electrically resistive element to complete the electrofusion; means for generating a voltage from the power supply; and means for transmitting the voltage to the electrically resistive element.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.